Telephone system



A9151 1939- J. JEDRYCHOWSKI 2,152,889

TELEPHONE SYSTEM Filed May 28, 1936 Patented Apr. 4, 1939 UNITED STATESPATENT OFFICE Panstwowe Zaklady Tole-i Radjotechniczne W. Warszawie,Warsaw, Poland Application May 28,

1936, Serial No. 82,262

In Poland May 31, 1935 6 Claims.

This invention relates to automatic or semiautomatic telephone and liketelecommunicating or signalling systems with line finders.

Exchanges with line finders are known, in

which the subscribers lines are fitted with two individual relays: aline relay and a cut-oif relay. The line relay is used for marking thecalling line in line finder banks and for creating the start circuit.The cut-off relay serves for disconnecting the line relay when thecalling line has been found, and for interruption in this way the startcircuit.

There are also known exchanges, in which the two above-named relays arereplaced by one two step relay. But the working of such two-step relaysis less sure than that of normal relays, and the two-step relays requirea more frequent and diflicult periodical regulation.

The object of this invention is to provide an automatic orsemi-automatic exchange with line finders for the purpose oftele-communication, in which the creating of the start circuit, and theinterrupting of it after finding the calling line by the line finder, iseffected without any individual relay. In this way the calling lines inan exchange according to the invention must be fitted-apart from thearrangements explained in the following specification-with a normalone-step relay, only marking the calling line in the line finder banksin the case where such a marking is necessary in the supposed system ofexchange.

In an exchange according to the invention, the calling lines are fittedwith two individual rectifiers. The corresponding electrodes of theserectifiers are connected parallelly to each other for a group of thesubscribers lines, and annexed to the common branch containing the startrelay in such a way, that when a subscribers' call is made, a currentflows in the common branch, in the rectifiers appertaining to thecalling subscriber, and in the line appertaining to him. In this way thecommon start relay is excited and it mobilizes the line finder.

The line finder having found the calling subscriber, its brushes a and bare connected to the source of current feeding the connecting circuitsof the exchange. According to the invention, the plus pole of the sourcefeeding the subscriber station, when thecall is made, has a potentiallower than the potential of the plus pole in the source feeding thesubscriber lines during speaking, and the minus pole of the sourcefeeding the lines, when the call is made, has a potential higher thanthe potential of the minus pole of the source feeding the subscriberslines during speaking,

the direction of the current flowing through the subscribers linesduring speaking being the same as it was at the moment when thesubscribers call was made.

At the moment when the line finder stops in the calling line, therearises-due to the explained system of potentialsin the rectifiers adifference of potentials opposite to that which causes the flowing ofthe current, and the rectifiers, appertaining to this line, cease toconduct the current and the start relay becomes demagnetized andinterrupts the start circuit (when no other call has been made at thesame time).

The invention is characterized by the feature that the line is insulatedduring speaking against the influence of the common branch, containingthe start relay, by a suitable polarization of the rectifiers.

In this way the line is secured during speaking against cross-talks fromother circuits.

In exchanges which are not exchanges for the purpose of telephony, thewords subscribers and subscribers lines means any other analogoussuitable individual arrangements.

The telephone exchange described below with reference to theaccompanying drawing, serves as an example of one of the possibleapplications of this invention. The invention may, however, also beapplied to any other signalling exchanges.

The single figure represents a scheme of a part of an automatictelephone exchange necessary for understanding the invention. A1, A2 andA3 are subscribers apparatus, r1, 7'1, 1'2, r2, rs and r3'theresistances connected in series to the lines from the apparatus to theexchange, P11, Prl', PM, PM, Pm and Pr3'-the rectifying elementsconnected between the individual subscribers lines and the common pointsV3 and V2 in series with the winding of the relay U. The means formarking the calling line in the field of the contacts of the line finderbeing generally known, this detail has been omitted in the drawing.

The manner of drawing the rectifiers is such that the current flows fromthe higher potential on the side of the blade to the lower one ontheside of the plate, but at the lower potential on. the side of theblade, and the higher one on the side of the plate, the rectifier has avery high resistance and the current practically does not flow.

In the example given the following inequalities are forthcoming betweenthe potentials V1, V2, V3 and V4: potential of the point V2 is higherthan potential of the point V1, that of V3 is higher than that of V2 andthat of V4 is higher than that of V3; the following values are acceptedfor the above potentials: potential of the point V2=8 volts, potentialof the point V3=16 volts, potential of the point V4=24 volts, and thepotential of the point V1 is zero.

At the moment when one of the subscribers, e. g. A1 lifts the hand set,the following circuit is closed: the point V3, rectifier Pr1, resistancer1, subscribers apparatus A1, resistance 11', recs tifier Pr1, windingof the relay U, the point V2. Between the points V3 and V2 there is thetension=8 volts (equal to the. difierence of potentials of the points V3and V1).

Both rectifiers are connected on this circuit in the conductingdirection and, therefore, the current flows and the relay U operates.The relay U closes the circuit for the line finder SW which finds bymeans of the wipers a and b the called subscriber and stops there. Thecircuits of the operation and stopping of the line finder are omitted inthis description as they are known, and as these circuits perform theauxiliary functions only and do not form a part of this invention. 1

At the moment when the line finder stops at the called subscriber, theright and left windings of the feeding relay Z are connected parallellywith the points X1 and X1 through the already coupled contacts of thetest relay PS of the line finder. The relay Z is connected to thebattery having a tension V4=24 volts (equal to the difference ofpotentials of the points V4 and V1).

Parallelly to the last mentioned circuit, the following circuit isformed: Point V4, right winding of the relay Z, contacts l2 of the relayPS, Wiper and contact a of the finder SW, resistance r1, subscribersapparatus A1, resistance r1, contact and wiper b of the finder SW,contacts 3-4 of the relay PS, left winding of the relay Z, and point V1.

The values of the resistances T1 and T1 are selected in such a mannerthat the potential at the point X1 is higher than the potential at thepoint V3=16 volts, and the potential at the point -X1' is lower than thepotential of the point V2=8 volts.

In view of this, there are such potentials at the rectifying elements atwhich no current can flow through these elements, and, therefore, thelast described circuit may be regarded as disconnected from the commonpoints and will not react to any influences resulting from themechanical connection with these points.

At the moment, when, after selecting a demanded set, e. g. As, the testrelay PW of the line selector will operate, the called subscriber willlift the handset and a speech circuit will be closed, the potentials atthe points X1 and X1 will be changed, because of the connection to thewindings of the relay Z of a following parallel circuit: the point V4,right winding of the relay Z, contacts 5--5 of the relay PW, wiper andcontact g of the selector WL, resistance 13, subscribers apparatus A3,resistance r3, contact and wiper h of the selector WL, contacts 7-8 ofthe relay PW, left winding of the relay Z, and point V1.

Besides, the speech currents are flowing in the following circuit:subscribers apparatus A1, resistance r1, contact and wiper a of thefinder SW, contacts 2-! of relay PS, contacts 5-45 of the relay PW,wiper and contact 9 of the selector WL, resistance r3, subscribersapparatus A3, resistance r3, contact and wiper h of the selector WL,contacts '!----8 of the relayPW, contacts 4-3 of the relay PS, wiper andcontact b of the finder SW, resistance 11, apparatus A1.

The values of the resistances r1, T1, T3 and T3 are selected in such amanner that at very short subscribers lines and the highest possibleintensity of the voice on the microphones, the potentials at points X1,X1, X3 and X3 should not be equalized with the potentials on the otherside of the rectifying elements.

In the example given, as above noted, the tension of the feeding storagebattery was assumed to be equal to 24 volts at the battery terminals and8 volts and 16 volts at the points or terminals V2 and V3.

It is clear that depending on varying conditions,

these values may be changed in a manner which is the most suitable foreach separate case.

I claim:

1. In an automatic telephone and signalling exchange having linefinders, the sub-combination of: subscriber lines; rectifiers throughwhich said subscriber lines are connected in parallel with one another;a common relay to which said subscriber lines are connected; a currentsource feeding current to said relay; a current sourcefeeding current tosaid subscriber lines individually during suitable working periods, theplus pole of the first mentioned current source having a lower potentialthan the potential of the plus pole of the second mentioned currentsource, whilst the minus pole of the first mentioned current source hasa higher potential than the minus pole of the second mentioned currentsource, the rectifiers being so connected that the current flows fromthe plus pole of the first-mentioned current source to the minus pole ofsaid source.

2. In a semi-automatic telephone and signalling exchange having linefinders, the sub-combination of: subscriber lines; rectifiers throughwhich said subscriber lines are connected in parallel with one another;a common relay to which said subscriber lines are connected; a currentsource feeding current to said relay; a current source feeding currentto said subscriber lines individually during suitable working periods,the plus pole of the first mentioned current source having a lowerpotential than the potential of the plus pole of the second mentionedcurrent source, whilst the minus pole of the first mentioned currentsource has a higher potential than the minus pole of the secondmentioned current source, the rectifiers being so connected that thecurrent flows from the plus pole of the first mentioned current sourceto the minus pole of said source 3. In an automatic telephone andsignalling exchange having line finders, the sub-combination of:subscriber lines; rectifiers through which said subscriber lines areconnected in parallel with one another; a common relay towhich saidsubscriber lines are connected; a current source feeding current to saidrelay; a current source feeding current to said subscriber linesindividually during suitable working periods, this first mentionedcurrent source being a part of the second mentioned current source, theplus pole of the first mentioned current source having a lower potentialthan the potential of the plus pole of the second mentioned currentsource, whilst the minus pole of the first mentioned current source hasa higher potential than the minus pole of the second mentioned currentsource, the rectifiers being so connected that the current flows fromthe plus pole of the first mentioned current source to the minus pole ofthe said source.

iii)

4. In a semi-automatic telephone and. signalling exchange having linefinders, the sub-combination of: subscriber lines; rectifiers throughwhich said subscriber lines are connected in parallel with one another;a common relay to which said subscriber lines are connected; a currentsource feeding current to said relay; a current source feeding currentto said subscriber lines individually during suitable working periods,this first mentioned current source being a part of the second mentionedcurrent source, the plus pole of the first mentioned current sourcehaving a lower potential than the: potential of the plus pole of thesecond mentioned current source, Whilst the minus pole of the firstmentioned current source has a higher potential than the minus pole ofthe second mentioned current source, the rectifiers being so connectedthat the current flows from the plus pole of the first mentioned currentsource to the minus pole of said source.

5. An automatic telephone and signalling exchange arrangement havingline finders as specified in claim 1, wherein feeding relays for theindividual devices'are provided, each winding of the relays beingconnected during suitable working periods, in series with individualdevices, to the current source feeding current to the subscribers linesindividually during those periods, and said devices are connected withsaid rectifiers through resistances of such magnitude that when thecurrent is at its maximum value in said independent circuits the voltagedrop in each winding of said relays is smaller than the differencebetween the potential of the poles of said feeding device feedingcurrent to said independent circuits, and the potential of therespective poles of said feeding device feeding said common part.

6. A send-automatic telephone and signalling exchange arrangement havingline finders as specified in claim 2 wherein feeding relays for theindividual devices are provided, each winding of the relays beingconnected during suitable working periods, in series with individualdevices, to the current source feeding current to the subscribers linesindividually during those periods, and said devices are connected withsaid rectifiers through resistances of such magnitude that when thecurrent is at its maximum value in said independent circuits the voltagedrop in each Winding of said relays is smaller than the Iliiferencebetween the potential of the poles of said feeding device feedingcurrent to said independent circuits, and the potential of therespective poles of said feeding device feeding said common part.

JERZY J EDRYCHOWSKI.

